During intense athletic activities such as those which involve sprinting, jogging and other forms of running tremendous impact forces are experienced by the foot as it bears the entire burden of the athlete's weight each time it encounters the ground. In the sport of long distance running, in particular, such impact shock upon the foot may over a prolonged period, cause repeated number of injuries to the bones, muscles, joints, ligaments and tendons of the foot and leg. Recently, because of increased interest in physical fitness, and running in particular, the problem of foot and leg injuries has become acute and widespread. Remedies have focused upon more effective warm-up (e.g. calisthenics) techniques and improved equipment (e.g. running and other athletic shoe) design. Stress injuries to feet and legs persist, however.
The midsole or upper sole presently employed by the typical athletic shoe does not exhibit both optimal shock resistance and stability control. As the midsole is made of a softer material, (e.g. foam), its shock absorbent qualities are enhanced but stability and control are lost. This occurs because a certain proportion of the impact shock is transmitted up the bone structure to the ankle, causing it to wobble. Harder materials, (e.g. rubber), are more stable (less shock transmitted to the ankle), but result in more of the impact shock being absorbed directly by the foot.
The present invention has overcome the basic shortcomings of the prior art by providing an improved durable, lightweight shock resistant shoe sole which utilizes one or more inverted cups dispersed within the outersole or bottom sole which has its cup-shaped cavity penetrate the upper or midsole sole to such a degree that the upper sole plays essentially no part in absorbing shock at the natural contact point during a footstep. Such a shoe sole is an enhanced version of the shoe sole described by the inventor in U.S. Pat. No. 4,494,321.
It is an object of this invention to provide a high-strength shoe sole which incorporates therein impact absorbing inverted shock cups of a variety of shapes and configurations in order to maximize usage of the soles.
It is a further object of this invention to provide a high-strength shoe sole which provides impact absorbing inverted cups in a variety of locations within the sole to increase its effectiveness in absorbing shock and decrease its weight.
It is still another object of this invention to provide a high-strength shoe sole which provides impact absorbing inverted cups at a variety of preselected orientations with respect to the axis of the foot to increase its effectiveness in absorbing shock.
It is even a further object of this invention to provide a high-strength shoe sole which provides impact absorbing inverted cups having reinforcing means associated therewith to increase the durability thereof.
It is still a further object of this invention to provide a high-strength shoe sole which provides visibility of the impact absorbing inverted cups while adding structural support thereto.